In recent years, numerous attempts have been made to extract the vast quantities of energy that are contained in the oceans' waves. Studies by Gerstner in the early 1800's described in general terms the very large amounts of energy available, and postulated the mechanisms by which such waves were formed. Attention has heretofore focused on deep ocean waves having significant wave height; i.e., greater than 4 feet (1.25 m.). The most common devices have utilized wave following apparatus in which a piston or float is moved relative to a cylinder or other floats respectively. The relative motion is merely caused by the rise and fall of the wave. Such devices have also required waves which exhibit relatively constant characteristics of uniform wave height and generally constant direction of motion of the wave front. Additionally, for proper exploitation, such waves required a relatively constant period of motion. Period of motion is also referred to as frequency, which is determined by the length of time that it takes the crest or highest point of the wave to pass a fixed point in space and continuing until the next wave crest is encountered. The second wave crest is encountered only after a low point, called the trough, has passed the same fixed point. The height of the wave is considered to be the vertical distance between the water surface in the trough and the water surface at the crest. Significant improvements have been made over the simple wave follower type of device. Amplification and multiplication of the energy recoverable from waves is disclosed in the U.S. Pat. Nos. 4,355,511 and 4,563,591 to Jones.
Although the above methods and devices are suitable for extracting wave energy near shore, they are most effective when the waves encountered are of a substantially constant wave-form, as described above. Most proposed methods of wave energy extraction have avoided the problems of surf where the available wave height is much less and the waves do not exhibit a constant waveform. The velocity of a wave slows as it approaches the shore, the speed going to zero at the shore line. A wave, which exhibits hydraulic effects below the trough, is affected by the bottom near shore. Energy is dissipated against the bottom by friction and in the "breaking" of the wave. However, significant energy remains available until the velocity does go to zero. Additionally, such energy, once extracted is available closer to the locations it is needed than is energy extracted deep ocean waves.
Therefore, there is need for a method and apparatus for implementing and practicing such method for extracting in useable and reliable amounts the energy available in near-shore waves and surf.